VMware, an EMC subsidiary whose software lets multiple operating systems run on the same computer, is expected to announce next week that it will begin giving away one of its key products for free, CNET News.com has learned.

The company sells three core products, VMware Workstation, GSX Server and ESX Server, but competition is on the horizon in a market VMware once had to itself. On Monday, however, the company is expected to announce it will give away GSX for free, sources familiar with the plan said. GSX runs on a "host" Windows or Linux operating system and then lets "guest" operating systems run atop it in compartments called virtual machines. The higher-end ESX product, in contrast, needs no host and runs below the operating system layer.

VMware may gain two advantages from the move. First, because virtual machines can be moved from GSX to ESX, customers who try the former may choose to upgrade to the latter. Second, giving the software away for free could make VMware's technology more popular and cement the company's lead over emerging rivals.